There has been two other Delta Sigma Theta Fraternities:
One is the aforementioned pharmeceutical fraternity founded in 1915 at the Brooklyn College of Pharmacy (I think that's the name).
The other is a Christian fraternity now named Sigma Theta Epsilon that was originally named Delta Sigma Theta after a merger between the Phi Tau Theta and Sigma Epsilon Theta fraternities. The DST sorority threatened lawsuit for use of their name (see page 105 or 125 of In Search of Sisterhood and the STE fraternity history webpage at
http://www.sigmatheta.org/history.shtml ). This org was officially known as Delta Sigma Theta from 1941 to 1949.
I guess there's something about the name Delta Sigma Theta.